1. Field of the Invention
The present invention relates to a method for forming high pore volume alumina materials that also have relatively large average pore diameters. More particularly, the present invention relates to a process for increasing the macroporosity of an alumina by treatment of the alumina with an aqueous solution of an organic acid.
2. Description of the Prior Art
Alumina is a known article of commerce. High purity alumina is widely employed as the support or carrier in various catalyst compositions. Many methods are employed for the preparation and/or purification of catalyst grade alumina. Prior art workers have also disclosed processes for treating alumina materials with various acids. For example, Leach in U.S. Pat. No. 3,846,540 discloses a treatment of low porosity alumina with an aqueous solution of a monofunctional acid followed by precipitation with a base. Graulier in U.S. Pat. No. 3,628,914 discloses treating pellets of alumina with an aqueous medium of an organic or inorganic acid at a temperature greater than 100.degree. C.
It has now been found that changes in the pore structure of alumina particularly an increase in the macroporosity, that is, in the porosity and pore volume in larger pores, can be effected by treatment with an aqueous solution of certain organic acids.